Dynamically shifting control word

ABSTRACT

A method for generating a plurality of control words, each control word controlling access to an object. The method includes providing a control word packet (CWP), generating a first control word (CW) from the CWP, providing a second CW generation input and producing a second CW based, at least in part, on both of the following the first CW and the second CW generation input. Control word generating apparatus for generating a plurality of control words is also disclosed.

FIELD OF THE INVENTION

The present invention relates to conditional access in general, and inparticular to conditional access systems for use in data broadcastingand related data applications.

BACKGROUND OF THE INVENTION

Systems for scrambling a television data stream are well-known in theart. One such system is described in the following U.S. Pat. No.5,282,249 to Cohen et al.; U.S. Pat. No. 5,481,609 to Cohen et al.Scrambled television data streams described in the Cohen et al patentscomprise both scrambled data representing television signals and codedcontrol messages, also known as ECMs. The ECMs of Cohen et al comprise,in a coded form, data necessary for generating a control word (CW) whichmay be used to descramble the scrambled data representing televisionsignals. An ECM is also termed a control word packet or CWP.

Data necessary for generating a control word is known in the prior artto take many different forms and may include, in general, at least anyof the following: a control word; an encrypted control word packet whichis intended to be decrypted before use; and a seed to a generatingfunction such as, for example, a one-way function which generates thecontrol word upon input of the seed. Throughout the presentspecification and claims the terms “control word generating information”and “CW generating information” are used interchangeably to designatedata necessary for generating a control word in any appropriate form, asdescribed above.

While the two patents to Cohen et al describe an analog system, that is,a system in which analog television data streams are broadcast totelevision sets, it is appreciated that similar ECM methods may also beused for digital television data streams. Generally, the scramblingtechniques used for scrambling analog television signals such as, forexample, the well-known “cut-and-rotate” technique, are chosen for theirapplicability to analog signals. In scrambling of digital televisionsignals other scrambling techniques, well-known in the art, are used,the techniques being more appropriate to digital signals such as, forexample, applying the well-known DES algorithm to the digital televisionsignals.

Methods of transmitting a scrambled digital signal, including ECMs, aredescribed in the MPEG-2 standard, ISO/IEC 13818-6, 12 Jul. 1996 andsubsequent editions.

The system of Cohen et al and other systems described in the art share afeature of broadcasting an ECM synchronous to, generally immediatelybefore or in a data stream parallel to, the actual scrambled broadcast.Typically, such an ECM is valid for a brief duration, with a new ECMbeing broadcast, in synchrony with a scrambled broadcast scrambledaccording to a new key, a few seconds, such as 10 seconds, after thebroadcast of the previous ECM. Some systems have been described in whicha key is sent, whether by broadcasting or by other means such as bymail, with a lower frequency, even as low as once a month. Such a systemis described, for example, in U.S. Pat. No. 4,484,027 and Re 33,189 toLee et al.

Patents describing systems related to encrypted broadcasting and/or keydistribution in encrypted broadcasting systems include the following:

U.S. Pat. No. 4,228,321 to Flanagan describes a privacy transmissionsystem with remote key control, in which key control signals areproduced at the unscrambling location and are both used for unscramblingat that location and also transmitted to a scrambling location for usein scrambling.

U.S. Pat. No. 4,531,020 to Wechselberger et al describes a method forcontrolling the simultaneous broadcast of enciphered digital informationsignals, for example in a radio or television broadcast environment, toa plurality of subscribers using several levels of enciphering keys.

U.S. Pat. No. 4,531,021 to Bluestein et al describes enciphering digitalinformation for transmission using a first key, common to all receivers,and a second key specific to one receiver of a small group of receivers.

U.S. Pat. No. 4,864,615 to Bennett et al describes a system forreproduction of secure keys by using distributed key generation data anda distributed encrypted prekey.

U.S. Pat. No. 4,866,770 to Seth-Smith et al describes a system fordistributing video, audio, teletext, and data, in which system wide,individual decoder and group decoder control signals are transmitted aspart of a composite signal. The group decoder control signal includesinformation relating to a group of decoders, while the individualdecoder control signal includes information relating to the operation ofindividual decoders.

U.S. Pat. No. 4,944,006 to Citta et al describes a secure data packettransmission system utilizing a global encryption key as well as addresskeys for encrypting individually addressed bit packets.

U.S. Pat. No. 5,301,247 to Rasmussen et al describes a method forensuring secure communications, in which two keys are combined togetherto produce a session key.

U.S. Pat. No. 5,499,298 to Narasimhalu et al describes a method forcontrolled dissemination of digital information, in which encrypteddigital information is decrypted by a tamper-proof controlledinformation access device. Access to said tamper-proof controlledinformation access device is provided according to conditions specifiedby an information provider.

In general, methods of transmitting a scrambled digital signal,including ECMs, are well known. Some systems use a composite signal,that is, an analog or digital signal including a plurality ofcomponents. Typically the plurality of components includes both ascrambled television signal component and an ECM component, the ECMcomponent comprising a plurality of ECMs. Prior art references whichdiscuss examples of this type of signal include the following: DVBETR289, “Digital Video Broadcasting (DVB): Support for use of scramblingand conditional access (CA) within digital broadcasting systems”; andDVB SIM061, “Technical specification of DVB-Simulcrypt”, 1 Apr. 1997.

Other documents relating to broadcasting of digital information includethe DVB Specification for Data Broadcasting, document SI-DAT 360 (TM1779), 12 Feb. 1997; and ATSC Digital Television Standard, document A54,October 1995 and subsequent editions.

Other methods of transmitting a scrambled digital signal, particularlyuseful in a case where the signal includes sub-signals encoded accordingto various different methods, are described in “Common InterfaceSpecification for Conditional Access and other Digital VideoBroadcasting Decoder Applications”, DVB document A017, May 1996 andsubsequent editions; and in “Common Interface Specification forConditional Access and other Digital Video Broadcasting DecoderApplications”, CENELEC EN50221:1997.

European Patent Application EP 0 375 539 to Guillon et al describes aprocess which includes access messages when emitting composite videosignals, unscrambling the resulting signals using a smart card reader,whereby the smart card comprises encoded digital data, and utilizing aninteractive process for the identification of a digital signature.

European Patent Application EP 0 461 029 to Jouet et al describes atranscontroller device that is intended for an installation conformingto a MAC/PACKET standard.

PCT Patent Application WO 99/45711 to Sered et al describes a keydelivery method for use in an encoded communications system in which atleast one encoded item including a first item encoded with a first itemcontrol word is sent in a communication stream from a sender to areceiver. The method described includes transmitting an item entitlementcontrol message (IECM) comprising item control information, transmittinga stream entitlement control message (SECM) comprising stream controlinformation, and combining at least part of the item control informationand at least part of the stream control information to produce the firstitem control word.

U.S. Pat. No. 6,178,242 to Tsuria describes a digital recordingprotection system using ECMs.

The disclosure of U.S. Provisional Patent Application 60/206,056, fromwhich the present application claims priority, is hereby incorporatedherein by reference.

GB Patent 2 326 004 to Bauminger et al describes a viewer responsemethod for use with an interactive telecommunications system. The methodincludes accumulating a user interaction history of a user of thesystem. The user interaction history includes user interactioninformation associated with a plurality of user interaction events; andprovides user-sensible feedback, based at least in part on the userinteraction history.

The disclosures of all references mentioned above and throughout thepresent specification are hereby incorporated herein by reference.

MPEG-4, the most recent edition of the MPEG standard, enables thebroadcaster to manipulate video objects independently of each other. TheMPEG-4 standard does not address the issue of conditional access at thelevel of objects.

SUMMARY OF THE INVENTION

The present invention seeks to provide an improved conditional accesssystem and particularly a conditional access system useful forcontrolling a plurality of objects.

The term “digital data stream,” as used throughout the presentspecification and claims, refers in a broad sense to any stream ofdigital data transmitted continuously at least during a particularperiod of time, and particularly includes broadcast digital data such asbroadcast digital television signals.

The term “scrambling” in all of its forms, as used throughout thepresent specification and claims, refers to any appropriate method ofscrambling, encoding, or encrypting data, many such methods beingwell-known in the art.

The term “display” in all of its forms, as used throughout the presentspecification and claims, is not limited to visual presentation, butincludes making palpable to the senses or producing any appropriatesensible representation.

Applying principles known in the prior art, it would be straightforwardto deliver one ECM, to generate one CW, per object.

In a preferred embodiment, the present invention seeks to provideapparatus and methods for generating more than one CW from a single ECM.

Preferably, in the present invention, one or more appropriatetransformations are provided for producing a first CW and subsequent CWsfrom a single ECM.

It is appreciated that each individual CW may control one object or maycontrol a so-called “mega-object” which is comprised of a plurality ofobjects.

There is thus provided in accordance with a preferred embodiment of thepresent invention a method for generating a plurality of control words,each control word controlling access to an object, the method includingproviding a control word packet (CWP), generating a first control word(CW) from the CWP, providing a second CW generation input, and producinga second CW based, at least in part, on both of the following: the firstCW and the second CW generation input.

Further in accordance with a preferred embodiment of the presentinvention each control word controls access to a plurality of objects.

Still further in accordance with a preferred embodiment of the presentinvention the method also includes utilizing the first CW to controlaccess to a first object, and utilizing the second CW to control accessto a second object.

Additionally in accordance with a preferred embodiment of the presentinvention the method also includes providing a third CW generationinput, and producing a third CW based, at least in part, on both of thefollowing: the second CW and the third CW generation input.

Moreover in accordance with a preferred embodiment of the presentinvention the third CW generation input includes a user input.

Further in accordance with a preferred embodiment of the presentinvention the third CW generation input includes a user characteristicinput associated with a user.

Still further in accordance with a preferred embodiment of the presentinvention the user characteristic input includes at least one of thefollowing: an indication of a geographic region associated with theuser, an indication of urban/rural dwelling associated with the user, anindication of a preference associated with the user, an indication of anage category associated with the user, an indication of an ageassociated with the user, an indication of a gender associated with theuser, and an indication of an ethnic identity associated with the user.

Additionally in accordance with a preferred embodiment of the presentinvention the method also includes receiving a data stream wherein thefirst object and the second object are included in the data stream.

Moreover in accordance with a preferred embodiment of the presentinvention the data stream includes a broadcast data stream.

Further in accordance with a preferred embodiment of the presentinvention the data stream includes an MPEG data stream.

Further in accordance with a preferred embodiment of the presentinvention the MPEG data stream includes an MPEG-4 data stream.

Still further in accordance with a preferred embodiment of the presentinvention the first object and the second object includes a displayobject.

Additionally in accordance with a preferred embodiment of the presentinvention the display object includes a visual display object.

Moreover in accordance with a preferred embodiment of the presentinvention each of the first object and the second object includes anaccumulative display object.

Further in accordance with a preferred embodiment of the presentinvention each of the first object and the second object includes anexclusive display object.

There is also provided in accordance with another preferred embodimentof the present invention a method for generating a second control wordfrom a first control word, the first control word controlling access toa first object and the second control word controlling access to asecond object, the method including providing a first control word (CW),providing a second CW generation input, and producing a second CW based,at least in part, on both of the following: the first CW and the secondCW generation input.

Further in accordance with a preferred embodiment of the presentinvention each control word controls access to a plurality of objects.

Still further in accordance with a preferred embodiment of the presentinvention the second CW generation input includes a user input.

Additionally in accordance with a preferred embodiment of the presentinvention the second CW generation input includes a user characteristicinput associated with a user.

Moreover in accordance with a preferred embodiment of the presentinvention the user characteristic input includes at least one of thefollowing: an indication of a geographic region associated with theuser, an indication of urban/rural dwelling associated with the user, anindication of a preference associated with the user, an indication of anage category associated with the user, an indication of an ageassociated with the user, an indication of a gender associated with theuser, and an indication of an ethnic identity associated with the user.

Further in accordance with a preferred embodiment of the presentinvention the first object and the second object are included in thedata stream.

Still further in accordance with a preferred embodiment of the presentinvention the data stream includes a broadcast data stream.

Additionally in accordance with a preferred embodiment of the presentinvention the data stream includes an MPEG data stream.

Moreover in accordance with a preferred embodiment of the presentinvention the MPEG data stream includes an MPEG-4 data stream.

Further in accordance with a preferred embodiment of the presentinvention each of the first object and the second object includes adisplay object.

Still further in accordance with a preferred embodiment of the presentinvention the display object includes a visual display object.

Additionally in accordance with a preferred embodiment of the presentinvention each of the first object and the second object includes anaccumulative display object.

Moreover in accordance with a preferred embodiment of the presentinvention each of the first object and the second object includes anexclusive display object.

There is also provided in accordance with another preferred embodimentof the present invention, a method for generating a plurality of controlwords, each control word controlling access to an object, the methodincluding providing a control word packet (CWP), generating a firstcontrol word (CW) from the CWP, providing a second CW generation input,producing a second CW based, at least in part, on both of the following:the first CW and the second CW generation input, utilizing the first CWto control access to a first object, utilizing the second CW to controlaccess to a second object, providing a third CW generation input,producing a third CW based, at least in part, on both of the following:the second CW and the third CW generation input, and utilizing the thirdCW to control access to a third object.

Further in accordance with a preferred embodiment of the presentinvention each control word controls access to a plurality of objects.

There is also provided in accordance with another preferred embodimentof the present invention, a method for generating a plurality of controlwords, each control word controlling access to an object, the methodincluding providing a first control word (CW), providing a second CWgeneration input, producing a second CW based, at least in part, on bothof the following: the first CW and the second CW generation input,utilizing the first CW to control access to a first object, utilizingthe second CW to control access to a second object, providing a third CWgeneration input, producing a third CW based, at least in part, on bothof the following: the second CW and the third CW generation input, andutilizing the third CW to control access to a third object.

Further in accordance with a preferred embodiment of the presentinvention each control word controls access to a plurality of objects.

Still further in accordance with a preferred embodiment of the presentinvention at least one of the second CW generation input and the thirdCW generation input includes a user input.

Additionally in accordance with a preferred embodiment of the presentinvention the method also includes displaying at least the second objectand the third object.

Moreover in accordance with a preferred embodiment of the presentinvention the displaying includes displaying the first object.

Further in accordance with a preferred embodiment of the presentinvention the method also includes providing an event associated withthe first object, the second object, and the third object, anddetermining a price for the event.

Still further in accordance with a preferred embodiment of the presentinvention the price is based, at least in part, on at least one of thesecond CW generation input and the third CW generation input.

There is also provided in accordance with another preferred embodimentof the present invention a method for generating a plurality of controlwords, each control word controlling access to an object, the pluralityof control words including a first control word and at least oneadditional control word, the method including providing a first controlword (CW), setting a variable V equal to the first CW, for eachadditional CW to be generated, performing the following steps: providingan additional CW generation input, producing an additional CW based, atleast in part, on both of the following: V, and the additional CWgeneration input, and setting the variable V equal to the additionalcontrol word.

Further in accordance with a preferred embodiment of the presentinvention each control word controls access to a plurality of objects.

Still further in accordance with a preferred embodiment of the presentinvention the providing a first CW includes providing a control wordpacket (CWP), generating the first CW from the CWP.

There is also provided in accordance with another preferred embodimentof the present invention a method for generating a plurality of controlwords, each control word controlling access to an object, the pluralityof control words including a first control word and at least oneadditional control word, the method including providing a first controlword (CW), for each additional CW to be generated, performing thefollowing: steps providing an additional CW generation input, andproducing an additional CW based, at least in part, on both of thefollowing: the first CW, and the additional CW generation input.

Further in accordance with a preferred embodiment of the presentinvention each control word controls access to a plurality of objects.

Still further in accordance with a preferred embodiment of the presentinvention the providing a first CW includes providing a control wordpacket (CWP), and generating a first control word (CW) from the CWP.

Additionally in accordance with a preferred embodiment of the presentinvention each object includes a scrambled object, and each CW includesa key for descrambling the scrambled object associated therewith.

Moreover in accordance with a preferred embodiment of the presentinvention each control word controls access to a plurality of objects.

There is also provided in accordance with another preferred embodimentof the present invention, a method for providing a multiple-questiongame in a data broadcast environment, the method including providing afirst scrambled question, providing a first control word (CW) includingdescrambling information for descrambling the first question, receiving,from a user, a first answer to the first question, and producing asecond CW based, at least in part, on both of the following: the firstCW and the first answer, the second CW including descramblinginformation for descrambling a second question.

Further in accordance with a preferred embodiment of the presentinvention at least one of the first question and the second questionincludes a plurality of questions.

There is also provided in accordance with another preferred embodimentof the present invention, control word generating apparatus forgenerating a plurality of control words, each control word controllingaccess to an object, the control word generating apparatus including acontrol word generator for generating a first control word (CW) from acontrol word packet (CWP), and a control word processor for producing asecond CW based, at least in part, on both of the following: the firstCW and a second CW generation input.

Further in accordance with a preferred embodiment of the presentinvention the apparatus includes a security subsystem, which includes atleast one of the following: the control word generator, and the controlword processor.

Still further in accordance with a preferred embodiment of the presentinvention the security subsystem includes a removable security element,which includes at least one of the following: the control wordgenerator, and the control word processor.

There is also provided in accordance with another preferred embodimentof the present invention, control word generating apparatus forgenerating a second control word from a first control word, the firstcontrol word controlling access to a first object and the second controlword controlling access to a second object, the control word generatingapparatus including a control word processor for producing a second CWbased, at least in part, on both of the following: a first CW and asecond CW generation input.

There is also provided in accordance with another preferred embodimentof the present invention, control word generating apparatus forgenerating a plurality of control words, each control word controllingaccess to an object, the control word generating apparatus including acontrol word generator for generating a first control word (CW) from acontrol word packet (CWP), a control word processor for producing asecond CW based, at least in part, on both of the following: the firstCW and a second CW generation input, and an object access controller forutilizing the first CW to control access to a first object and thesecond CW to control access to a second object, wherein the control wordprocessor is operative to produce a third CW based, at least in part, onboth of the following: the second CW and a third CW generation input,and the object access controller is operative to utilize the third CW tocontrol access to a third object.

Further in accordance with a preferred embodiment of the presentinvention the apparatus includes a security subsystem, which includes atleast one of the following: the control word generator, the control wordprocessor, and the object access controller.

Still further in accordance with a preferred embodiment of the presentinvention the security subsystem includes a removable security element,which includes at least one of the following: the control wordgenerator, the control word processor, and the object access controller.

There is also provided in accordance with another preferred embodimentof the present invention control word generating apparatus forgenerating a plurality of control words, each control word controllingaccess to an object, the control word generating apparatus including acontrol word processor for producing a second CW based, at least inpart, on both of the following: a first CW and a second CW generationinput, and an object access controller for utilizing the first CW tocontrol access to a first object and the second CW to control access toa second object, wherein the control word processor is operative toproduce a third CW based, at least in part, on both of the following:the second CW and a third CW generation input, and the object accesscontroller is operative to utilize the third CW to control access to athird object.

Further in accordance with a preferred embodiment of the presentinvention the apparatus also includes a security subsystem, whichincludes at least one of the following: the control word processor, andthe object access controller.

Still further in accordance with a preferred embodiment of the presentinvention the security subsystem includes a removable security element,which includes at least one of the following: the control wordprocessor, and the object access controller.

There is also provided in accordance with another preferred embodimentof the present invention, control word generating apparatus forgenerating a plurality of control words, each control word controllingaccess to an object, the plurality of control words including a firstcontrol word and at least one additional control word, the control wordgenerating apparatus including a control word processor receiving afirst control word (CW) as input and operative to set a variable V equalto the first CW, for each additional CW to be generated receive anadditional CW generation input, produce an additional CW based, at leastin part, on both of the following: V, and the additional CW generationinput, and set the variable V equal to the additional control word.

There is also provided in accordance with another preferred embodimentof the present invention, control word generating apparatus forgenerating a plurality of control words, each control word controllingaccess to an object, the plurality of control words including a firstcontrol word and at least one additional control word, the control wordgenerating apparatus including a control word processor receiving thefirst control word (CW) and operative, for each additional CW to begenerated, to receive an additional CW generation input, and produce anadditional CW based, at least in part, on both of the following: thefirst CW, and the additional CW generation input.

Further in accordance with a preferred embodiment of the presentinvention the apparatus also includes a security subsystem, whichincludes the control word processor.

Still further in accordance with a preferred embodiment of the presentinvention the security subsystem includes a removable security element,which includes the control word processor.

There is also provided in accordance with another preferred embodimentof the present invention, game apparatus for providing amultiple-question game in a data broadcast environment, the apparatusincluding a scrambled question descrambler receiving a first scrambledquestion and a first control word (CW) including descramblinginformation for descrambling the first question and operative todescramble the first question, and a control word processor receiving,from a user, a first answer to the first question and operative toproduce a second CW based, at least in part, on both of the following:the first CW and the first answer, the second CW including descramblinginformation for descrambling a second question.

Further in accordance with a preferred embodiment of the presentinvention the apparatus also includes a security subsystem, whichincludes at least one of the following: the scrambled questiondescrambler, and the control word processor.

Still further in accordance with a preferred embodiment of the presentinvention the security subsystem includes a removable security element,which includes at least one of the following: the scrambled questiondescrambler, and the control word processor.

Additionally in accordance with a preferred embodiment of the presentinvention the removable security element includes a smart card.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description, taken in conjunction with thedrawings in which:

FIG. 1A is a simplified partly pictorial, partly block diagramillustration of a control word generating system constructed andoperative in accordance with a preferred embodiment of the presentinvention;

FIG. 1B is a simplified pictorial illustration of a control device,useful in understanding the operation of the system of FIG. 1A;

FIG. 1C is a simplified partly pictorial, partly block diagramillustration of the system of FIG. 1A, useful in understanding theoperation thereof;

FIG. 1D is a simplified pictorial illustration of the control device ofFIG. 1B, useful in understanding FIG. 1C;

FIG. 1E is a simplified partly pictorial, partly block diagramillustration of the system of FIG. 1A, useful in understanding theoperation thereof;

FIG. 1F is a simplified pictorial illustration of the control device ofFIG. 1B, useful in understanding FIG. 1E;

FIG. 2A is a simplified partly pictorial, partly block diagramillustration of a control word generating system constructed andoperative in accordance with an alternative preferred embodiment of thepresent invention;

FIG. 2B is a simplified pictorial illustration of a control device,useful in understanding the operation of the system of FIG. 2A;

FIG. 2C is a simplified partly pictorial, partly block diagramillustration of the system of FIG. 2A, useful in understanding theoperation thereof;

FIG. 3A is a simplified partly pictorial, partly block diagramillustration of a control word generating system constructed andoperative in accordance with another preferred embodiment of the presentinvention;

FIG. 3B is a simplified pictorial illustration of a control device,useful in understanding the operation of the system of FIG. 3A;

FIG. 3C is a simplified partly pictorial, partly block diagramillustration of the system of FIG. 3A, useful in understanding theoperation thereof;

FIG. 3D is a simplified pictorial illustration of the control device ofFIG. 3B, useful in understanding FIG. 3C;

FIG. 3E is a simplified partly pictorial, partly block diagramillustration of the system of FIG. 3A, useful in understanding theoperation thereof;

FIG. 3F is a simplified pictorial illustration of the control device ofFIG. 3B, useful in understanding FIG. 3E;

FIG. 4A is a simplified partly pictorial, partly block diagramillustration of a control word generating system constructed andoperative in accordance with a further preferred embodiment of thepresent invention;

FIG. 4B is a simplified pictorial illustration of a control device,useful in understanding the operation of the system of FIG. 4A;

FIG. 4C is a simplified partly pictorial, partly block diagramillustration of the system of FIG. 4A, useful in understanding theoperation thereof;

FIG. 5 is a simplified flowchart illustration of a preferred method ofoperation of the systems of FIGS. 1A-1F, 2A-2C, 3A-3F, and 4A-4C;

FIG. 6 is a simplified flowchart illustration of an alternativepreferred method of operation of the systems of FIGS. 1A-1F, 2A-2C,3A-3F, and 4A-4C;

FIG. 7 is a simplified flowchart illustration of a further alternativepreferred method of operation of the systems of FIGS. 1A-1F and 3A-3F;

FIG. 8 is a simplified flowchart illustration of a still furtheralternative preferred method of operation of the systems of FIGS. 1A-1Fand 3A-3F;

FIG. 9 is a simplified flowchart illustration of another alternativepreferred method of operation of the systems of FIGS. 1A-1F and 2A-2C;

FIG. 10 is a simplified flowchart illustration of a further alternativepreferred method of operation of the systems of FIGS. 3A-3F and 4A-4C;and

FIG. 11 is a simplified flowchart illustration of another alternativepreferred method of operation of the systems of FIGS. 1A-1F and 3A-3F.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

In the drawings of the present application, similar reference numbersare used to refer to similar elements. For the sake of brevity andclarity of description, repeated description of similar elements isgenerally omitted.

Reference is now made to FIG. 1A which is a simplified partly pictorial,partly block diagram illustration of a control word generating systemconstructed and operative in accordance with a preferred embodiment ofthe present invention.

The system of FIG. 1A, generally designated 100, preferably comprisesthe following components, each of which may be implemented in a suitablecombination of hardware and software, as is well known in the art:

1. Control word packet and control word (CWP/CW) processing apparatus110, preferably operative to receive a CWP 120 and to produce therefrom,as described in detail below, a plurality of control words (CWs). Afirst control word (CW1) 130 is shown in FIG. 1A by way of example only.

2. Scrambled object unscrambling apparatus 140, preferably operative toreceive a control word (CW), such as the CW1 130 and a scrambled objectsuch as a first scrambled object (SO1) 150, and to produce therefrom afirst unscrambled object (UO1) 160. Preferably, scrambled objectunscrambling apparatus 140 uses appropriate mechanisms well known in theart to produce the UO1 160 from the SO1 150 and the CW1 130.

For example, and without limiting the generality of the foregoing, in asystem using DES as a scrambling method, the SO1 150 preferablycomprises an object scrambled using DES, the CW1 130 comprises a DES keyfor unscrambling the SO1 150, and the UO1 160 comprises the result ofdescrambling the SO1 150 using the DES descrambling method well known inthe art and the DES key comprised in the CW1 130.

It is appreciated that many possible appropriate scrambling systems areknown in the art, and that a person reasonably skilled in the art wouldbe able to adapt the present invention for use with any appropriatescrambling system.

A datastream of scrambled objects 165 comprising a plurality ofscrambled objects including SO1 150 is preferably input into scrambledobject unscrambling apparatus 140

3. Unscrambled object display apparatus 170, which may comprise anyappropriate apparatus for making the UO1 160 visible or otherwisesensible to one or more human senses. For purposes of simplicity ofillustration and without limiting the generality of the foregoing,unscrambled object display apparatus 170 is shown in FIG. 1A as atelevision set which, as is well known in the art, typically comprisesapparatus for making unscrambled input visible and audible. Unscrambledobject display apparatus 170 will be referred to herein as television(TV) 170 or display 170, it being appreciated that any other appropriatetype of unscrambled object display apparatus may alternatively oradditionally be used.

4. The system of FIG. 1A also preferably comprises a set top box (STB)175, which may comprise any appropriate set top box or integratedreceiver/decoder (IRD), as is well known in the art, suitably programmedto provide a user interface as described herein. It is appreciated that:the STB 175 may or may not include a removable security element such asa smart card (not shown); and the functionality of the STB 175 mayalternatively be included within the TV 170, in which case the STB 175may be omitted.

As is well known in the art, the STB 175 is preferably operativelyassociated with the TV 170 and is preferably operative to receive and,where appropriate, decode television transmissions.

Preferably, as is also well known in the art, the STB 175 is equippedwith a return path or other ability to communicate with a broadcaster, abroadcaster headend, or another appropriate location (not shown).

It is well known in the art that various types of return path areavailable, and that an appropriate return path should be chosen. Forexample, in the case of a cable broadcast, where the STB 175 isappropriate for receiving cable broadcasting, the return path maycomprise a cable return path. In the case of a satellite broadcast,where the STB 175 is appropriate for receiving satellite broadcasting,the return path may comprise a telephone return path, also known as a“telephone link”. It is appreciated that other technologies forimplementing a return path, including but not limited to VSAT satellitereturn path technology, are known, and that any appropriate return pathmay be used.

Preferably, but not necessarily, CWP/CW processing apparatus 110 andscrambled object unscrambling apparatus 140 are comprised in the STB 175or in a removable security element, such as a smart card, operativelyassociated therewith; those elements are shown separately in thedrawings of the present application for purposes of simplicity andclarity of description.

One example of a system comprising a set top box with removable securityelement is described in U.S. Pat. No. 6,178,242 to Tsuria, thedescription of which is hereby incorporated herein by reference.

The operation of the system of FIG. 1A is now briefly described. Thecontrol word packet 120 is processed by CWP/CW processing apparatus 110to generate the CW1 130.

Control words, such as the CW1 130, are input into scrambled objectunscrambling apparatus 140 and are used to unscramble correspondingscrambled objects from the datastream of scrambled objects 165. Withinthe scrambled object unscrambling apparatus 140, the CW1 130 is used tounscramble the SO1 150 to produce the UO1 160 for display on the TV 170as a display object 1 (DO1) 180.

It is appreciated that the UO1 160 is in the form of data, preferablydigital data; the UO1 160 is shown in FIG. 1A displayed on the TV 170 asthe DO1 180.

The source of the datastream of scrambled objects 165 including the SO1150 could be a broadcast, a DVD disk, a VCR tape, a floppy disk, anattached hard drive, a magnetic tape, or any other appropriate source(none of which are shown) as is well known in the art.

Control words are generated, preferably by a smart card (not shown)which is associated with the STB 175. Logical values which are input viathe user, the datastream 165, a user profile or any other means as iswell known in the art may preferably be stored in a memory of the smartcard.

In the case where there is user input, the user presses on a controldevice, such as a control device 190 (FIG. 1B). The STB 175 registersthat the user pressed a certain value and then the STB passes thecertain value to the smart card. The smart card preferably stores thecertain value that was passed to the smart card in the smart card'smemory.

Smart card memory can be non-volatile, retaining data when not connectedto an external power supply, or volatile, not retaining data when notconnected to an external power supply. Non-volatile memory sources knownin the art include EEPROM, EPROM, flash memory, ROM, and battery backedRAM. Volatile memory sources known in the art include RAM and dataregisters.

In the present invention, the smart card preferably takes the valueentered by the user from the smart card's memory and uses that value asan input to generate the next control word.

Reference is now additionally made to FIG. 1B, which is a simplifiedpictorial illustration of a control device, useful in understanding theoperation of the system of FIG. 1A.

A user preferably interacts with the system 100 in FIG. 1A. Thus, theuser, via a control device 190, interacts with the STB 175 by respondingto output displayed on the TV 170 via the control device 190. Userinterfaces of this general type are well known in the art.

It is appreciated that many types of appropriate user interface are wellknown, and that the depiction of the control device 190 in FIG. 1B isnot meant to be limiting.

The control device 190 may comprise any appropriate control devicesuitable for use with the STB 175; for example, if the STB 175 isadapted to receive infrared control signals of a certain type, theremote control 190 is preferably adapted to produce signals of thattype. The control device preferably includes a plurality of controls200.

The user, in the example of FIG. 1A, sees the DO1 180 which includes aquestion. In FIG. 1B, the user uses the control device 190 by selectingat least one of the plurality of controls 200 to respond to the questionwhich is displayed on the TV 170.

In FIG. 1B, by way of example, the user inputs the correct answer to thequestion posed in the D01 180 by entering “1” via the control device190.

The example of FIGS. 1A and 1B is a user interaction interface; it isappreciated that the present invention is not limited to userinteraction and can be based on other input including input suppliedfrom a prestored user profile, which can be permanently associated witha particular user or which can be established at the beginning of eachsession.

For example, and without intending to limit the generality of theforegoing, a prestored user profile may include information regardingregion, ethnicity, an urban/rural dwelling indicator, user preferences,age, age category, and gender.

For example and without intending to limit the generality of theforegoing, user information may be used to change the appearance ofobjects on the TV 170. A “vehicle” object can be either a car or a truckdepending on an “urban/rural” region indicator. The “person” objectdriving the vehicle can be Jewish, Italian, Polish, Hispanic, Asian,African American etc. depending on the “ethnic” indicator. The “sky”object can be sunny or snowy depending on the “climate” indicator.

Reference is now additionally made to FIG. 1C which is a simplifiedpartly pictorial, partly block diagram illustration of the system ofFIG. 1A, useful in understanding the operation thereof.

FIG. 1C shows use of the user's correct response, input in FIG. 1B, todynamically generate a second control word (CW2) 230 and reveal anadditional object on the display.

In FIG. 1C, the CW1 130 and a first input (I1) 210 are processed byCWP/CW processing apparatus 110 to generate a second control word (CW2)230. CWP/CW processing apparatus 110 preferably generates the CW2 230through appropriate mathematical manipulation of its inputs, comprisingthe CW1 130 and the I1 210.

Any appropriate mathematical manipulation or operation can be applied tothe inputs or to values derived from the inputs.

For example, and without limiting the generality of the foregoing:appropriate mathematical operations include XOR, OR, AND, NOT, NAND,NOR, and XNOR.

For example, and without limiting the generality of the foregoing: ifthe I1 210 is a one-byte value and the CW1 130 is an 8-byte value, theI1 210 can be applied via any appropriate mathematical operation to anybyte of the CW1 130 to generate a value that can be used to derive theCW2 230 through further appropriate mathematical manipulation.

Alternatively an 8-byte value derived from the I1 210 can be generatedby duplicating the value of the I1 in 8-bytes to create an 8-byte valuederived from the I1 210. The 8-byte value derived from the I1 210 canthen be used in a mathematical operation with the CW1 130 to generatethe CW2 230.

Further alternatively the I1 210 and the CW1 130 can be used toinitialize a one-way function to generate the CW2 230.

Still further alternatively the I1 210 and the CW1 130 can be used asinputs to a one-way function to generate the CW2 230.

Alternatively shifting the CW1 130 by a value derived from the I1 210can be used to generate the CW2 230.

Individual bytes or individual bits of the CW1 130 can be shifted by avalue derived from the I1 210 or by the value of the I1 210 itself.Shifting in which shifted bits wrap around and fill bits vacated byshifting may be used. Shifting in which empty spaces created by shiftingare consistently filled with “0”s or consistently filled with “1”s maybe used. Shifting may be done to the right or to the left of the valuethe CW1 130.

Further alternatively shifting the I1 210 by a value derived from theCW1 130 can be used to generate the CW2 230.

The mathematical operations discussed above are by way of example onlyand are not meant to be limiting.

CW1 130 and CW2 230 are used by way of example only in the abovediscussion. Control word generation for all subsequent control words maypreferably be generated in a similar manner.

A method which iteratively offsets each successive control word by avalue derived from the most recent user input can be used to generatethe next control word in sequence. Such a method for generatingsuccessive control words is illustrated in FIGS. 1A-1F, as describedherein.

An alternative method iteratively offsets a variable equal to CW1 by avalue derived from the most recent user input to generate the nextcontrol word in sequence.

Within scrambled object unscrambling apparatus 140, the CW2 230 is usedto unscramble a second scrambled object (SO2) 240 to produce a secondunscrambled object (UO2) 250. It is appreciated that the UO2 250 is inthe form of data and is displayed, preferably as a discrete object, onthe TV 170 as a second display object (DO2) 260. DO1 180 and DO2 260 arepreferably simultaneously displayed on the TV 170.

Reference is now additionally made to FIG. 1D, which is a simplifiedpictorial illustration of the control device 190 of FIG. 1B, useful inunderstanding FIG. 1C.

In FIG. 1C, the DO2 260 includes a question which solicits user input.The user preferably interacts with the control device 190 in FIG. 1D bypressing at least one control from the plurality of controls 200 toenter a response to the question posed by the DO2 260.

In FIG. 1D, by way of example, the user inputs the correct answer to thequestion posed in the D02 260, by entering “2” via the control device190.

Reference is now additionally made to FIG. 1E which is a simplifiedpartly pictorial, partly block diagram illustration of the system ofFIG. 1A, useful in understanding the operation thereof.

FIG. 1E shows use of the user's correct response, input in FIG. 1D, todynamically generate a third control word (CW3) 270 which reveals anadditional object on the display 170.

In FIG. 1E, the CW2 230 and a second input (I2) 265 are processed byCWP/CW processing apparatus 110 to generate the third control word (CW3)270. Within the scrambled object unscrambling apparatus 140, the CW3 270is used to unscramble a third scrambled object (SO3) 290 to produce athird unscrambled object (UO3) 300. It is appreciated that the UO3 300is in the form of data and is then displayed, preferably as a discreteobject, on the TV 170 as a third display object (DO3) 310. The DO1 180,the DO2 260, and the DO3 310 are preferably simultaneously displayed onthe TV 170.

Reference is now additionally made to FIG. 1F, which is a simplifiedpictorial illustration of the control device 190 of FIG. 1B, useful inunderstanding FIG. 1E.

In FIG. 1E, the DO3 310 includes a question which solicits user input.The user preferably interacts with the control device 190 in FIG. 1F bypressing at least one control from the plurality of controls 200 toenter a correct response to the question posed by the DO3 310.

In FIG. 1F, by way of example, the user inputs the correct answer to thequestion posed in the D03 310, by entering “1” via the control device190.

The correct input can be used in combination with the CW3 270 togenerate a fourth control word (not shown) in the same manner that theCW2 230 and the CW3 270 were generated. The process for generatingcontrol words from one CWP 120 as described in FIGS. 1A-1F is iterativeand can continue until the application is completed, assuming that allof the responses that the user enters are correct. It is alsoappreciated, in accordance with the above description that iterative theCW 130 generation can occur a minimum of twice, once to generate the CW1130 and once to generate the CW2 230.

Reference is now made to FIG. 2A which is a simplified partly pictorial,partly block diagram illustration of a control word generating systemconstructed and operative in accordance with an alternative preferredembodiment of the present invention.

The operation of the system of FIG. 2A is now briefly described. Thecontrol word packet 120 is processed by the CWP/CW processing apparatus110 to generate the CW1 130. Within the scrambled object unscramblingapparatus 140, the CW1 130 is used to unscramble the SO1 150 to producethe UO1 160 for display on the TV 170 as the DO1 180.

It is appreciated that the UO1 160 is in the form of data, preferablydigital data; the UO1 160 is shown in FIG. 2A displayed on the TV 170 asthe DO1 180.

Reference is now additionally made to FIG. 2B, which is a simplifiedpictorial illustration of the control device 190 of FIG. 1B, useful inunderstanding the operation of the system of FIG. 2A. A user preferablyinteracts with the system 100 and thus with the TV 170 via the controldevice 190.

In FIG. 2A, the user sees the DO1 180 which includes a question.

In FIG. 2B, the user uses the control device 190 by selecting at leastone of the plurality of controls 200 to incorrectly respond to thequestion which is displayed on the TV 170.

The example of FIGS. 2A and 2B is a user interaction interface; it isappreciated that the present invention is not limited to userinteraction and can be based on other input including unsuitable ornon-matching input supplied from a prestored user profile, as describedabove, which can be permanently associated with a particular user orwhich can be established at the beginning of each session.

Reference is now made to FIG. 2C which is a simplified partly pictorial,partly block diagram illustration of the system of FIG. 2A, useful inunderstanding the operation thereof.

FIG. 2C shows how the user's incorrect response, a third input (I3) 320,is used to generate an erroneous CW 330. The erroneous CW 330 is a CWwhich indicates to the system that unsuitable or non-matching input hasbeen received. The erroneous CW 330 does not unscramble the nextscrambled object in sequence. The erroneous CW 330 preferably causes anerror message to be generated.

When the user enters a value, an explicit status is preferably returnedto the software element that indicates whether the user entered acorrect or incorrect response. For example, a method can be built into asmart card which indicates that the response input by the user is valid.Such methods are well known in the art and include digital signaturesand checksums. When the explicit status registers an incorrect status,the erroneous CW 330 is generated.

Generating CW1 330 when the explicit status registers an incorrectstatus is by way of example only. When an incorrect status is registeredin the explicit status, an error message can be generated in any otheracceptable manner including the software breaking the generation ofcontrol words without an erroneous CW 330.

The erroneous CW 330 cannot be used to unscramble the SO2 240 and anerror message 340 is generated instead. The error message 340 isdisplayed on the TV 170 as a display error 350. DO1 180 and the displayerror 350 are preferably simultaneously displayed on the TV 170.

The user is unable to proceed in the displayed interactive applicationbecause the previous control word is needed to generate the next controlword in sequence.

It is further appreciated that, in embodiments where inputs are notinteractively provided by a user, an incorrect input may halt subsequentcontrol word generation, or may not halt subsequent word generation. Anincorrect input and resultant generation of the erroneous CW 330 ispreferably noted and acted upon in the conditional access system in somemanner such as sending an error message back to the broadcaster orprinting out an error message on the TV 170.

Reference is now made to FIG. 3A, which is a simplified partly pictorialpartly block diagram illustration of a control word generating systemconstructed and operative in accordance with another preferredembodiment of the present invention.

The operation of the system of FIG. 3A is now briefly described. Thecontrol word packet 120 is processed by CWP/CW processing apparatus 110to generate the CW1 130. Within the scrambled object unscramblingapparatus 140, the CW1 130 is used to unscramble the SO1 150 to producethe UO1 160 for display on the TV 170 as the DO1 180.

It is appreciated that the UO1 160 is in the form of data, preferablydigital data; the UO1 160 is shown in FIG. 3A displayed on the TV 170 asthe DO1 180.

By way of example, the DO1 180 is shown as occupying part of the screen.The DO1 180 could also occupy the entire screen. By way of example, DO1180 is illustrated as a stationary display object. The DO1 180 couldalso be a dynamic video object which moves across the screen. The DO1180 could also have associated audio or subtitle information.

Reference is now additionally made to FIG. 3B, which is a simplifiedpictorial illustration of a control device, useful in understanding theoperation of the system of FIG. 3A. A user preferably interacts with thesystem 100 and thus with the TV 170 via the control device 190.

In FIG. 3A, the user sees the DO1 180 which includes a question. In FIG.3B, the user uses the control device 190 by selecting at least one ofthe plurality of controls 200 to respond to the question which isdisplayed on the TV 170.

The example of FIGS. 3A and 3B is a user interaction interface; it isappreciated that the present invention is not limited to userinteraction and can be based on other input including input suppliedfrom a prestored user profile, as described above, which can bepermanently associated with a particular user or which can beestablished at the beginning of each session.

The operation of the embodiment of the invention, as described by FIGS.3A-3F, outputs display objects on the TV 170 one at a time. Each displayobject is exclusively displayed on the TV 170, as opposed to beingdisplayed accumulatively, where all display objects are simultaneouslydisplayed.

The operation of the system of FIG. 3A is now briefly described.

In FIG. 3A, the DO1 180 is exclusively displayed on the TV 170.

In FIG. 3B, the user inputs the correct answer to the question posed inthe D01 180 by entering “1”via the control device 190.

Reference is now made to FIG. 3C which is a simplified partly pictorial,partly block diagram illustration of the system of FIG. 3A, useful inunderstanding the operation thereof.

FIG. 3C shows use of the user's correct response, input in FIG. 3B, todynamically generate the CW2 230, produce the UO2 250, and display theDO2 260 instead of the DO1 180 on the TV 170. The DO2 260 is exclusivelydisplayed.

In FIG. 3C, the CW1 130 and a fourth input (I4) 355 are processed by aCWP/CW processing apparatus 110 to generate the second control word(CW2) 230. CWP/CW processing apparatus 110 preferably generates CW2 230through mathematical manipulation of its inputs, the CW1 130 and the I4355.

Possible means of accomplishing said manipulation is described abovewith reference to FIG. 1C.

Reference is now additionally made to FIG. 3D, which is a simplifiedpictorial illustration of the control device 190 of FIG. 3B, useful inunderstanding FIG. 3C. A user preferably interacts with the system 100and thus with the TV 170 via the control device 190.

In FIG. 3D, by way of example, the user inputs the correct answer to thequestion posed in the D02 260, by entering “2” via the control device190.

Reference is now additionally made to FIG. 3E which is a simplifiedpartly pictorial, partly block diagram illustration of the system ofFIG. 3A, useful in understanding the operation thereof.

FIG. 3E shows use of the user's correct response, input in FIG. 3D, todynamically generate the CW3 270, produce the UO3 300, and display theDO3 310 instead of the DO2 260 on the TV 170. The DO3 310 is exclusivelydisplayed.

In FIG. 3E, the CW1 130 and a fifth input (I5) 360 are processed byCWP/CW processing apparatus 110 to generate the CW3 270. Withinscrambled object unscrambling apparatus 140, the CW3 270 is used tounscramble the SO3 290 to produce the UO3 300. It is appreciated thatthe UO3 300 is in the form of data and is then displayed, preferably asa discrete object, on the TV 170 as the DO3 310.

Reference is now additionally made to FIG. 3F, which is a simplifiedpictorial illustration of the control device 190 of FIG. 3B, useful inunderstanding FIG. 3E.

In FIG. 3E, the DO3 310 includes a question which solicits user input.The user preferably interacts with the control device 190 in FIG. 3F bypressing at least one control from the plurality of controls 200 toenter a correct response to the question posed by the DO3 310.

In FIG. 3F, by way of example, the user inputs the correct response tothe question posed in the D03 310, by entering “1” via the controldevice 190.

This correct input can be used in combination with CW1 to generate afourth control word (not shown) in the same manner that CW2 and CW3 weregenerated. The process for generating control words from one CWP 120 asshown in FIGS. 3A-3F is iterative and can continue until the applicationis completed, assuming that all of the responses that the user entersare correct. It is also appreciated, in accordance with the abovedescription that iterative CW generation can occur a minimum of twice.

The system of FIGS. 3A-3F preferably operates on the same principles asthat of FIGS. 1A-1F with two exceptions:

1. In FIGS. 3A-3F, each display object is exclusively displayed on theTV 170. Each successive display object is displayed on the TV 170instead of the display object which had previously been displayed. InFIGS. 1A-1F all display objects are accumulatively displayed.

2. In FIGS. 3A-3F, successive control word generation utilizes the CW1130 as one of the inputs thereto. In FIGS. 1A-1F successive control wordgeneration utilizes the latest generated control word as one of itsinputs; for example, the CW2 230 is used as one of the inputs togenerate CW3 270.

It is appreciated that the exclusive display of objects on the TV 170and successive control word generation from a constant input, the CW1130, are shown together by way of example only and can be implementedseparately.

Reference is now made to FIG. 4A which is a simplified partly pictorial,partly block diagram illustration of a control word generating systemconstructed and operative in accordance with an alternative preferredembodiment of the present invention.

Reference is now additionally made to FIG. 4B which is a simplifiedpictorial illustration of a control device, useful in understanding theoperation of the system of FIG. 4A.

Reference is now additionally made to FIG. 4C which is a simplifiedpartly pictorial, partly block diagram illustration of the system ofFIG. 4A, useful in understanding the operation thereof.

FIGS. 4A-4C depict preferable operation of the system of FIG. 3A whenthe user inputs an incorrect response.

In FIG. 4A, the user sees the D01 180 which includes a question.

In FIG. 4B, the user uses the control device 190 by selecting at leastone of the plurality of controls 200 to incorrectly respond to thequestion which is displayed on the TV 170.

FIG. 4C shows use of the user's incorrect response, a sixth input (I6)380, to generate the erroneous CW 330. The erroneous CW 330 cannotunscramble the SO2 240 and the error message 340 is generated instead.The error message 340 is exclusively displayed on the TV 170 as thedisplay error 350. Display error 350 is displayed instead of DO1 180 onthe TV 170.

FIGS. 4A-4C operate on the same principles as FIGS. 2A-2C with theexception that each display object is exclusively displayed on the TV170. In FIGS. 4A-4C, each successive display object is output on the TV170 instead of the display object which had previously been displayed.In FIGS. 2A-2C, by contrast, all descrambled objects are accumulativelydisplayed.

It is further appreciated that in FIGS. 4A-4C, the user being unable toproceed in the displayed interactive application is by way of exampleonly. It is appreciated that the user may enter an incorrect responseand the application may continue. Because successive control wordgeneration is based on CW1 130, all subsequent keywords can begenerated, even when the previous control word was not generated. Evenin the case where the first input is incorrect, CW1 can come frominternal processing and subsequent control words can be generated.

Preferably, the user can continue even when an incorrect value isentered.

In FIG. 4C, the display error 350 is exclusively displayed on the TV170. The DO3 310, which was previously displayed, no longer appears onthe screen.

It is appreciated that the present invention, in the preferredembodiments as described above, may be used to implement a wide varietyof applications, preferably including entertainment applications.

For example, and without limiting the generality of the foregoing: in asports application, objects, representing elements of a sports event tobe shown on a TV screen, might be revealed one at a time in response tocorrect user inputs. It is further appreciated that a price or a prizemight be associated with such an application; for example, and withoutlimiting the generality of the foregoing, a user who answered allquestions correctly might be excused from payment, or a user whoanswered less than a predetermined minimum of questions correctly mightbe required to make a higher than normal payment.

It is appreciated that in the present invention, in the preferredembodiments as described above, in place of a control word packet, afirst control word can be a first input to the CWP/CW processingapparatus which begins the iterative generation of subsequent controlwords.

In another non-limiting example of an application which might beimplemented using the preferred embodiments described above, a first CWderived from a CWP might be used to enable display of, for example, amovie or a portion thereof. Second and subsequent CWs, produced asdescribed above, might be used for an interactive application,including, for example, one or more screen overlays, associated with themovie.

It is appreciated that, in various preferred embodiments, the presentinvention, which preferably utilizes one CWP to generate many CWs forcontrolling objects, may save an ample amount of bandwidth when comparedto a prior art system which would require one CWP for each CW.

Reference is now made to FIG. 5, which is a simplified flowchartillustration of a preferred method of operation of the systems of FIGS.1A-1F, 2A-2C, 3A-3F, and 4A-4C. The method of FIG. 5 is self-explanatorywith reference to the above description of FIGS. 1A-1F, 2A-2C, 3A-3F,and 4A-4C.

Reference is now made to FIG. 6, which is a simplified flowchartillustration of a preferred method of operation of the systems of FIGS.1A-1F, 2A-2C, 3A-3F, and 4A-4C. The method of FIG. 6 is self-explanatorywith reference to the above description of FIGS. 1A-1F, 2A-2C, 3A-3F,and 4A-4C.

Reference is now made to FIG. 7, which is a simplified flowchartillustration of a preferred method of operation of the systems of FIGS.1A-1F and 3A-3F. The method of FIG. 7 is self-explanatory with referenceto the above description of FIGS. 1A-1F and 3A-3F.

Reference is now made to FIG. 8, which is a simplified flowchartillustration of a preferred method of operation of the systems of FIGS.1A-1F and 3A-3F. The method of FIG. 8 is self-explanatory with referenceto the above description of FIGS. 1A-1F and 3A-3F.

Reference is now made to FIG. 9, which is a simplified flowchartillustration of a preferred method of operation of the systems of FIGS.1A-1F and 2A-2C. The method of FIG. 9 is self-explanatory with referenceto the above description of FIGS. 1A-1F and 2A-2C.

Reference is now made to FIG. 10, which is a simplified flowchartillustration of a preferred method of operation of the systems of FIGS.3A-3F and 4A-4C. The method of FIG. 10 is self-explanatory withreference to the above description of FIGS. 3A-3F and 4A-4C.

Reference is now made to FIG. 11, which is a simplified flowchartillustration of a preferred method of operation of the systems of FIGS.1A-1F and 3A-3F. The method of FIG. 11 is self-explanatory withreference to the above description of FIGS. 1A-1F and 3A-3F.

It is appreciated that, in typical CA systems known in the art, the CWchanges according to a predetermined schedule in which there is one CWfor every “key period”. It is known in the art, for example, to have a10 second key period and to transmit a plurality of CWPs, each CWP beingassociated with the same CW, during the key period; often, each CWPtransmitted during a given key period is identical to each other CWPtransmitted during that key period.

It is therefore appreciated that, in some preferred embodiments of thepresent invention, there may be a different CWP for each key period. Insuch preferred embodiments, correct inputs that were used to generateobjects during a first key period are preferably saved in the smartcard's memory. These saved values may then be used, in a second keyperiod, together with the new CWP, as explained above, to generate acorresponding sequence of CWs, which are then used to regenerate thepreviously displayed objects.

It is appreciated that various features of the invention which are, forclarity, described in the contexts of separate embodiments may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention which are, for brevity, described in thecontext of a single embodiment may also be provided separately or in anysuitable subcombination. For example exclusive display of objects on theTV 170 can be implemented independently of successive control wordgeneration using the CW1 130 as one of its inputs as discussed in FIGS.3A-3F.

It will be appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. Rather the scope of the invention is defined onlyby the claims which follow:

1-65. (canceled)
 66. A method for providing a multiple-question game,the method comprising: providing a first scrambled question; providing afirst control word (CW) including descrambling information fordescrambling the first question; receiving, from a user, a first answerto the first question; and producing a second CW based, at least inpart, on both of the following: the first CW and the first answer, thesecond CW including descrambling information for descrambling a secondquestion.
 67. The method according to claim 66 and wherein at least oneof the first question and the second question comprises a plurality ofquestions.
 68. Game apparatus for providing a multiple-question game,the apparatus comprising: a scrambled question descrambler receiving afirst scrambled question and a first control word (CW) includingdescrambling information for descrambling the first question andoperative to descramble the first question; and a control word processorreceiving, from a user, a first answer to the first question andoperative to produce a second CW based, at least in part, on both of thefollowing: the first CW and the first answer, the second CW includingdescrambling information for descrambling a second question.
 69. Theapparatus according to claim 68 and also comprising a securitysubsystem, and wherein the security subsystem comprises at least one ofthe following: the scrambled question descrambler; and the control wordprocessor.
 70. The apparatus according to claim 69 and wherein thesecurity subsystem comprises a removable security element, and theremovable security element comprises at least one of the following: thescrambled question descrambler; and the control word processor.
 71. Theapparatus according to claim 70 and wherein the removable securityelement comprises a smart card.
 72. Game apparatus for providing amultiple-question game, the apparatus comprising: scrambled questiondescrambling means for receiving a first scrambled question and a firstcontrol word (CW) including descrambling information for descramblingthe first question and operative to descramble the first question; andcontrol word processing means for receiving, from a user, a first answerto the first question and operative to produce a second CW based, atleast in part, on both of the following: the first CW and the firstanswer, the second CW including descrambling information fordescrambling a second question.